A tire typically includes plies of various types, including, for example, an inner ply. These plies may be formed from a long sheet of rubber stock material by cutting the stock material to appropriate lengths and folding the end portions together to form a generally annular shape adapted to become part of a tire carcass. The two end portions of the stock material are typically overlapped a small amount and may be bonded together, for example, by adhesively bonding, or "stitching" the end portions together under pressure. The overlap of the ply ends results in a limited circumferential portion of these plies having a slight radial buildup, which cannot be avoided with known cutting techniques.
Currently, when a sufficient length of stock material has been prepared for cutting, the stock material is supported on a processing table and the blade is forced into the material. The blade is moved across the width of the stock material to cut off the desired length of material. The stock material is typically formed from rubber based products which are flexible and "sticky" to the touch. When the stock material is being cut with a conventional blade, the material tends to move or vibrate as the blade traverses the material, thereby increasing the cutting time and decreasing the quality of the cut. Moreover, the blade must cut the stock material at an angle substantially perpendicular to the processing table, or the stock material will tend to bunch up in front of the blade. The perpendicular angle of cut results in a cut edge having a reduced surface area, thereby making it difficult to splice the cut surfaces to one another in the tire building process. Consequently, it is necessary to overlap the ply end portions a small amount and adhesively bond or "stitch" them together under pressure.
Other cutting techniques are generally known but have not been successfully applied to stock material cutting. For example, ultrasonic cutting has been used for cutting textile material as shown in U.S. Pat. No. 4,711,693 issued to Holze, Jr. The Holze patent shows an anvil comprising an elongated, substantially rectangular housing in which a piston is disposed for motion relative to the housing. The anvil includes a slitting implement advanced by the piston. The textile material is fed through the nip between the slitting implement and ultrasonic horn. The ultrasonic horn is undergoing vibratory motion to cut the textile material held thereagainst.
Additionally, it is known that attempts have been made to cut tire sidewall material with a conventional blade at angles as small as 23.degree. with respect to the horizontal, and then splice the cut ends together with a bevel lap splice. However, it has been found that a bevel lap splice of 23.degree. or more in a sidewall does not adhere well without additional glues or adhesives and can become separated under normal tire operating conditions.